Louis Hayet (29 August 1864, Pontoise – 27 December 1940, Cormeilles-en-Parisis) was a French Post-Impressionist painter.
He was able to study, briefly, at the École des Arts Décoratifs, but seems to have been largely self-taught; although he certainly benefitted from a friendship with Camille Pissarro and his son, Lucien, whom he had met while painting in the countryside.
As a result, Paul Signac removed his name from the second edition of his book, From Eugène Delacroix to Neo-impressionism (considered to be the manifesto of Pointillism).
Hayet's cousin, the Director of the École d'Alembert in Montévrain, hired him as a Professor of ornamental design; a post he held until 1911.
He would spend the last part of his career conducting scientific research on colors and pigments but, by the 1930s, he had given up painting and was in poor health.